A Sinn Féin TD has compared economists who warn of high initial costs for a united Ireland to climate change deniers.

Thomas Gould made the comparison during a Dáil debate on the tax and spending implications of unification. He accused some commentators of using unreliable data to block progress, and pointed to a 2024 study by Professor John Fitzgerald that estimated an annual cost of €11 billion. A rival estimate from Professor John Doyle put the figure nearer €2.5 billion.

Tánaiste Simon Harris cautioned against reducing the transition to a single number. He said the process would bring considerable cost and complexity, but the economic effects would be dynamic. Over time, he argued, costs and revenues would shift as the economies integrate and grow, with outcomes shaped by policy choices. The debate, he added, should focus on what can be built in both jurisdictions.

The exchange followed the defeat of a Sinn Féin bill that would have established a citizens’ assembly on unity and required a government green paper on preparations.